PLC breaker bridge

ABSTRACT

In accordance with certain embodiments consistent with the invention, a power line communication (PLC) bridge circuit, consistent with certain embodiments, has a first coupler that couples data signals to and from a main power line circuit. A second coupler couples data signals to and from a branch power line circuit, wherein the branch power line circuit is branched from the main power line circuit. A first communication transceiver is connected to the first coupler for transferring data signals to and from the first coupler. A second communication transceiver is connected to the second coupler for transferring data signals to and from the second coupler. A controller examines data signals from the first transceiver and determines if the data is destined for the second transceiver, so that data that is not destined for the second transceiver is considered local data. The controller also examines data signals from the second transceiver and determines if the data is destined for the first transceiver, so that data that is not destined for the first transceiver is also considered local data. A bridge passes data signals between the first communication transceiver and the second transceiver when the controller determines that the data is not local, and passes data signals between the first communication transceiver and the second communication transceiver when the controller determines that the data is local. This abstract is not to be considered limiting, since other embodiments may deviate from the features described in this abstract.

CROSS REFERENCE TO RELATED DOCUMENTS

This application is a continuation-in-part of U.S. patent applicationSer. No. 11/297,528 filed Dec. 8, 2005 which claims priority benefit ofU.S. Provisional Patent Application No. 60/645,900 filed Jan. 21, 2005,both of which are hereby incorporated by reference.

COPYRIGHT NOTICE

A portion of the disclosure of this patent document contains materialwhich is subject to copyright protection. The copyright owner has noobjection to the facsimile reproduction of the patent document or thepatent disclosure, as it appears in the Patent and Trademark Officepatent file or records, but otherwise reserves all copyright rightswhatsoever.

BACKGROUND

Home power lines usually use a single-phase three-wire system havingfirst and second “hot” lines L1, L2 and a neutral that sends power toeach home from a distribution transformer. Usually, several homes shareone distribution transformer. Power lines L1 and L2 are normally coupledtogether (and usually coupled to neighbors) via the distributiontransformer. Power line communication (PLC) networks utilize theexisting power lines in order to facilitate computer networking (ornetworking of other appliances such as audio/video equipment). In oneexample, networks using the HomePlug® standard are used for achievingPLC communication. Since such networks interconnect devices usingexisting power outlets, information traveling over the power line may beaccessible by neighbors or others tapping into the power line outsidethe home. If filtering is installed to prevent data from travelingoutside the home, the two lines L1 and L2 may be isolated from eachother.

In the case of global communication between lines L1 and L2, the signalmay travel a long distance and get attenuated. Although attenuation inglobal communication is often negligible, sometimes it is not and thusit requires high transmission power, which would cause interference toother electronic products. This basic problem is addressed in U.S.patent application Ser. No. 11/297,528, the parent of the presentapplication.

Powerline Communication (PLC) is expected to be used as a backbone ofhome networking. As of this writing, the second generation PLC standardis under discussion and will soon be finalized. The second generationPLC under discussion is a 200 Mbps class network. The actual payloadrate, however, is 50 to 60 Mbps. This second generation is beingproposed to simultaneously carry a few of MPEG-HD streams. Although thesecond generation PLC meets the present bandwidth requirements,bandwidth needs are likely to be ever increasing and more bandwidth willbe required when HDTV streaming becomes common.

BRIEF DESCRIPTION OF THE DRAWINGS

Certain illustrative embodiments illustrating organization and method ofoperation, together with objects and advantages may be best understoodby reference detailed description that follows taken in conjunction withthe accompanying drawings in which:

FIG. 1 is a diagram of a power line network consistent with certainembodiments of the present invention.

FIG. 2 is a flow chart depicting bridge operation consistent withcertain embodiments of the present invention.

FIG. 3 is a timing chart of an exemplary scheme for master bridge accessmanagement in a manner consistent with certain embodiments of thepresent invention.

FIG. 4 is a diagram of a power line network consistent with certainembodiments of the present invention.

FIG. 5 is a diagram of an access power line network consistent withcertain embodiments of the present invention.

FIG. 6 is a block diagram of a powerline bridge consistent with certainembodiments of the present invention.

FIG. 7 is a timing chart of an exemplary scheme for access management ina manner consistent with certain embodiments of the present invention.

FIG. 8 is a diagram illustrating potential cross-phase paths between L1and L2.

FIG. 9 is a block diagram of a cross-phase isolation filter consistentwith certain embodiments of the present invention.

FIG. 10 depicts a wireless bridge arrangement consistent with certainembodiments of the present invention.

FIG. 11 is a block diagram of an exemplary wireless powerline bridgeconsistent with certain embodiments of the present invention.

FIG. 12 illustrates exemplary powerline network consistent with certainembodiments.

FIG. 13 shows a block diagram of the internal components of an exemplaryPLC Bridge consistent with certain embodiments.

FIG. 14 shows the internal components of an exemplary main PLC unitconsistent with embodiments of the present invention.

FIG. 15 shows an alternative embodiment for the main PLC Bridgeconsistent with certain embodiments of the present invention.

DETAILED DESCRIPTION

While this invention is susceptible of embodiment in many differentforms, there is shown in the drawings and will herein be described indetail specific embodiments, with the understanding that the presentdisclosure of such embodiments is to be considered as an example of theprinciples and not intended to limit the invention to the specificembodiments shown and described. In the description below, likereference numerals are used to describe the same, similar orcorresponding parts in the several views of the drawings.

The terms “a” or “an”, as used herein, are defined as one or more thanone. The term “plurality”, as used herein, is defined as two or morethan two. The term “another”, as used herein, is defined as at least asecond or more. The terms “including” and/or “having”, as used herein,are defined as comprising (i.e., open language). The term “coupled”, asused herein, is defined as connected, although not necessarily directly,and not necessarily mechanically. The term “program” or “computerprogram” or similar terms, as used herein, is defined as a sequence ofinstructions designed for execution on a computer system. A “program”,or “computer program”, may include a subroutine, a function, aprocedure, an object method, an object implementation, in an executableapplication, an applet, a servlet, a source code, an object code, ashared library/dynamic load library and/or other sequence ofinstructions designed for execution on a computer system.

Reference throughout this document to “one embodiment”, “certainembodiments”, “an embodiment” or similar terms means that a particularfeature, structure, or characteristic described in connection with theembodiment is included in at least one embodiment of the presentinvention. Thus, the appearances of such phrases or in various placesthroughout this specification are not necessarily all referring to thesame embodiment. Furthermore, the particular features, structures, orcharacteristics may be combined in any suitable manner in one or moreembodiments without limitation.

The term “or” as used herein is to be interpreted as an inclusive ormeaning any one or any combination. Therefore, “A, B or C” means “any ofthe following: A; B; C; A and B; A and C; B and C; A, B and C”. Anexception to this definition will occur only when a combination ofelements, functions, steps or acts are in some way inherently mutuallyexclusive.

Powerline Network Bridge

As described in application Ser. No. 11/297,528, the parent of thepresent application, home power line usually uses a single-phasethree-wire system. Referring to FIG. 1, L1, L2 and neutral (elements 2,4 and 3 respectively) send power to each home from the distributiontransformer 1. For purposes of this document, each instance of L1 isconsidered a 120VAC circuit and each instance of L2 is considered a120VAC circuit, or simply “circuit”; and a 240VAC circuit is obtainedacross L1 and L2. Usually, several homes share distribution transformer1. Components 8 to 10 are powerline network devices, for example, aserver or a client. Components 11 and 12 are a load, for example, a roomheater or a lamp. When device 8 transmits data to device 10, the dataare sent through L1, and the communication is readily accomplished sinceit is a local communication using the same power line L1. However, whendevice 8 transmits data to device 9, the data arrives at its destinationby way of the distribution transformer 1 (L1→L2) (and in some instances,via cross-talk in breaker board 5 or through appliances representing a240 volt load from L1 to L2. This is referred to as a global (orcross-phase) communication. In this case, the signal may travel a longway and get attenuated. Attenuation is not generally negligible and themaximum transmission power is limited by the FCC rules. In manyinstances, global communication accounts for 70-80% of local (in-phase)communication bandwidth. Another issue is that L1 and L2 have to sharethe time or frequency bandwidth even though they are separate. That isfor example, device 9 on L2 cannot use the powerline network whiledevice 8 and 10 carry out local communication on L1. This is notbandwidth efficient. Certain embodiments consistent with the presentinvention can be utilized to solve these problems and others.

In accordance with certain embodiments consistent with the presentinvention, a low pass filter 6 and a bridge device 7 are the utilized.The low pass filter (blocking filter) 6 passes, for example, signalshaving frequency content below 100 kHz. Since powerline networksgenerally utilize signals of higher frequency than 100 kHz, thosesignals are blocked from passing outside the low-pass filter toward thebreaker board 5 and the distribution transformer 1. Such filter 6 shouldbe designed block all powerline signals, so that no signal goes outsideof the home. In addition to enhancing security, this further serves tominimize radiation of signals that can cause interference with otherelectronic devices. In addition, the filter 6 prevents unwanted signalsfrom entering the home, thereby preventing neighboring networks fromproducing interference with the network shown in FIG. 1. With filter 6,the in-home powerline is completely isolated from the outside. Suitableblocking filters are commercially available in the market, for example,from Power Plus Co., LTD, of Dublin, Ireland.

Bridge device 7 is provided in order to isolate L1 from L2. When thebridge 7 receives a local stream, for example, from device 8 to 10 onL1, the bridge does not forward the stream to L2. The bridge only sendsdata to the other power line when it receives a global stream from L1(or L2) to L2 (or L1). The bridge 7 internally has a device table andknows what device is on L1 or L2. Based on the device table, the bridge7 determines to send or not to send to the other power line. Because L1and L2 are isolated from each other, the total network bandwidth maytheoretically approach twice that of a network without the bridgearrangement disclosed herein. In practical cases, it is anticipated thatat least a 40-50% improvement can be achieved. (No global stream is thebest case. The full bandwidth of L1 and L2 can be available in eachnetwork respectively.)

An example of bridge 7 is depicted in block diagram form in FIG. 6, andwill be discussed later. The operation of bridge 7 is described inconnection with FIG. 2 starting at 30 after which the bridge 7determines if data have been received. If not, the bridge 7 awaitsreceipt of data. If data are received at 34, the bridge consults thedevice table for the destination at 38. If the destination is local, at42, no action is taken and the process returns to 34. If, however, thedestination is not in the same circuit as the source (not local, butcross-phase communication), the bridge 7 identifies a time slot (orcarrier frequency or other parameter depending upon the modulationscheme) at 46 available on the destination circuit in order to be ableto transmit the received data to the destination circuit at 50.

Referring now to FIG. 3, a timing diagram is used to illustrate theisolation between circuits using the present bridge arrangement. In thisillustration, a separate set of beacons 101 a and 102 a are used for thecircuit of L1, while beacons 101 b and 102 b are used in circuit L2.Data shown at 110 a are transferred as cross-phase communication to L2at 110 b in an available time slot. Similarly, data at 112 a aretransferred to 112 b in an available time slot. (The illustrated beaconsmay be synchronized to AC line cycle, usually 50 or 60 Hz, or handled inanother manner as will be described later.) Local communication trafficrepresented by 111 and 113 remain isolated as do the beacons. In thisillustration, the beacons are approximately synchronized, but thisshould not be considered limiting since they may be totally independentas will be described later. This timing diagram will be discussed ingreater detail later.

Office powerline distribution and distribution in large homes and otherinstallations serviced by multiple distribution transformers is morecomplicated than that used in most homes. In such environments,physically close outlets are not always on the same power line circuit,instead, they may be supplied via other distribution transformers.Hence, no power line networking is generally available between suchoutlets.

A bridge arrangement consistent with certain embodiments can be used tolink independent power lines. FIG. 4 shows an example of such an officepowerline distribution (or other system in which multiple distributiontransformers feed a single institution) in which a powerline network isdesired. In this case, two distribution transformers are illustrated.Transformer 201 provides power lines 202 and 204 along with a neutral203. The power passes through breaker board 205 and low pass filter 206in the same manner as described in connection with FIG. 1. Components208, 209 and 210 represent network nodes, while 211 and 212 representother loads on the power line circuit. Transformer 301 provides powerlines 302 and 304 along with a neutral 303. The power passes throughbreaker board 305 and low pass filter 306 in the same manner asdescribed in connection with FIG. 1. Components 308, 309 and 310represent network nodes, while 311 and 312 represent other loads on thepower line circuit. Bridge 207 links the two sets of the power lines.The bridge 207 forwards only global communications between two or morepower lines. Bandwidth of each power line can thereby be usedefficiently. While this can be accomplished using a wired connection aswill be described in connection with FIG. 6, wireless communication canalso be utilized to effect a portion of the bridging function.

Thus, a power line communication (PLC) bridge circuit consistent withcertain embodiments has a first coupler that couples data signals to andfrom the first power line circuit and a second coupler that couples datasignals to and from the second power line circuit. The first and secondpower line circuits are fed AC power from first and second distributiontransformers. A first communication transceiver is connected to thefirst coupler for transferring data signals to and from the firstcoupler. A second communication transceiver is connected to the secondcoupler for transferring data signals to and from the second coupler. Acontroller examines data signals from the first transceiver anddetermines if the data is destined for the second transceiver, whereindata that is not destined for the second transceiver is considered localdata. The controller further examines data signals from the secondtransceiver and determines if the data is destined for the firsttransceiver, wherein data that is not destined for the first transceiveris also considered local data. A bridge circuit passes data signalsbetween the first communication transceiver and the second transceiverwhen the controller determines that the data is not local, and for notpassing data signals between the first communication transceiver and thesecond communication transceiver when the controller determines that thedata is local.

In certain embodiments, a power line communication (PLC) bridging methodinvolves receiving data from a first power line circuit and a secondpower line circuit, wherein the first and second power line circuits arefed AC power from separate legs of a distribution transformer, and sharea single neutral connection; examining data signals from the first powerline circuit to determine if the data is destined for the second powerline circuit, wherein data that is not destined for the second powerline circuit is considered local data; examining data signals from thesecond power line circuit to determine if the data is destined for thefirst power line circuit, wherein data that is not destined for thefirst power line circuit is considered local data; passing data signalsbetween the first power line circuit and the second power line circuitwhen the data is determined to not be local; and not passing datasignals between the first power line circuit and the second power linecircuit when the controller determines that the data is local.

Referring now to FIG. 5, some companies plan to provide Internet accessservice using power lines as the communication medium. This is depictedin this figure wherein Transformer 401 provides power lines 402 and 404along with a neutral 403. The power passes through breaker board 405 andlow pass filter 406 in the same manner as described in connection withFIG. 1. Components 408, 409 and 410 represent network nodes, while 411and 412 represent other loads on the power line circuit. In thisembodiment, bridge 407 links the two sets of the power lines andforwards global communications between the two (or more) power lines,and further passes communications bound to or from the Internet aroundfilter 406 to facilitate Internet access.

In this case, the distribution transformer 401 passes no powerlinesignal. Jumper 420 is installed to the transformer to jump it and permitcommunication of Internet traffic. The bridge 407 links not only theinternal power lines L1′ and L2′, but also the incoming power lines L1and L2. The bridge 407 connects L1 (L2) to L1′ or L2′ on request. Inthis application, the bridge 407 may have more intelligence, forexample, router capability. The router can also act in the capacity of afirewall to protect the in-home powerline network from various attacksfrom the outside.

FIG. 6 illustrates an example block diagram of the bridge 7. Thoseskilled in the art will understand how to suitably modify this circuitto accommodate more circuits (as in FIG. 4 or FIG. 5). This exampleembodiment assumes as PLC network such as those conforming to theHomePlug® standard, or similar, but this should not be consideredlimiting since one of ordinary skill can adapt the present principles toother power line network arrangements. A signal from L1 is sent toAnalog Frontend (AFE) 502 through Coupler 501. Coupler 501 shuts out the120 VAC line voltage and only passes powerline network communicationsignals. The output of AFE 502 is analog-to-digital converted in A/D503. The result is processed in the physical layer block 505 and inMedia Access Control layer block 506.

When a signal is sent to L1, the signal is processed in the reversedirection. The signal is processed in MAC 506 and in PHY 505. The resultis digital-to-analog converted in D/A 504 and sent to AFE 502 andCoupler 501. Components 510, 511, 512, 513, 514 and 515 work for L2signals in a manner similar to that of components 501 to 506. CPU 508controls the PHY and MAC blocks (505, 506, 514 and 515) through theinternal bus 507. The internal bus 507 may be, for example, a PCI bus.CPU 508 executes the software program stored in the read only memory509. CPU 508 uses the random access memory 516 for temporary storage.The process depicted in FIG. 2 can be stored in ROM 509 or othercomputer readable storage medium and is carried out by execution ofinstructions on CPU 508.

When the data needs to be forwarded from L1 to L2, the output of MAC 506is sent to MAC 515 through the internal bus 507. If data buffering isrequired to facilitate correction of timing issues as described later,CPU 508 temporarily stores the data in RAM 516. Alternatively, theinternal memory in MAC 506 or 515 (not shown) may store the data.

Usually, regardless of local/global communications, the transmissionpower is fixed by federal regulation (e.g., the FCC). During globalcommunications, actual bandwidth would be reduced because of highersignal attenuation. The present PLC bridge prevents bandwidth reductionin most instances.

For purposes of this discussion, elements 502, 503, 504, 505, 506, 507,508, 509 and 516 operate together to constitute a data transceiver thatsends and receives data, via coupler 501, to and from power line circuitL1. Similarly, elements 511, 512, 513, 514, 515, 507, 508, 509 and 516operate together to constitute a data transceiver that sends andreceives data, via coupler 510, to and from power line circuit L2.Internal bus 507, along with processor (CPU) 508, utilizing ROM 509 andRAM 516 are shared between the two transceivers, with data passingbetween the two transceivers using internal bus 507, operating underprogram control with the program running on CPU 508. Hence, CPU 508serves in the capacity of a controller for the two (or more)transceivers.

Thus, a power line communication (PLC) bridge circuit consistent withcertain embodiments has a first coupler that couples data signals to andfrom the first power line circuit and a second coupler that couples datasignals to and from the second power line circuit. The first and secondpower line circuits are fed AC power from separate legs of adistribution transformer, and share a single neutral connection (orelse, are fed from multiple separate distribution transformers). A firstcommunication transceiver is connected to the first coupler fortransferring data signals to and from the first coupler. A secondcommunication transceiver is connected to the second coupler fortransferring data signals to and from the second coupler. A controllerexamines data signals from the first transceiver and determines if thedata is destined for the second transceiver, wherein data that is notdestined for the second transceiver is considered local data. Thecontroller further examines data signals from the second transceiver anddetermines if the data is destined for the first transceiver, whereindata that is not destined for the first transceiver is also consideredlocal data. A bridge circuit passes data signals between the firstcommunication transceiver and the second transceiver when the controllerdetermines that the data is not local, and does not pass data signalsbetween the first communication transceiver and the second communicationtransceiver when the controller determines that the data is local.

As described above, the bridge may control more than two power lines. Inthis case, a set of components 501 to 506 is implemented for each powerline. CPU 508 controls multiple streams through the internal bus 507.The internal bus 507 should be designed to have enough bandwidth tohandle the maximum number of streams contemplated for the particularapplication.

In order to facilitate access control, usually, a master exists on thepowerline network. The master receives an access request from a client(slave) and gives an access time (or frequency) slot to the client.Then, the client starts transmission. The master broadcasts a beaconperiodically. All transmissions are performed based on the beacon cycle.If contention-free transmission is required, the same access slot ineach beacon cycle is reserved for the transmission. In the case ofaccess with contention, an access slot is obtained onfirst-come-first-serve basis, or by use of other arbitration protocol.Assume that each of L1 and L2 has its own master. FIG. 7 illustratesaccess slot management by the bridge 7 (referring back to FIG. 1). TheL1 master sends beacon signals 601 and 602. The L2 master sends beacons603 and 604. L1 and L2 beacons are not synchronized in thisillustration. Slot 611 is used for local transmission on L1. Similarly,slots 613 and 614 are used for local transmission on L2. Slot 612 a is aglobal transmission from an L1 device to an L2 device. The bridge 7assigns the same slot 612 b on L2 to send the data to the finaldestination (L2 device). There is a little time delay between 612 a and612 b to forward the data in the bridge 7. The same slot is not alwaysavailable on L2. An L1 transmitter sends data using the slot 610 a.Unfortunately, the same time slot 613 on L2 is already occupied byanother local transmission. In this case, the bridge 7 finds anotherslot 610 b and forwards the data to the destination on L2. These actionscorrespond to the process depicted in block 46 of FIG. 2.

The bridge 7 may have master capability. In this case, no other masterexists either on L1 or on L2. All devices send an access request to thebridge 7. FIG. 3 illustrates access slot management in this case. Thebridge periodically sends beacons (101 and 102) to both L1 and L2. Theslots 110 and 112 are for global transmission. The slots 111 and 113 arefor local transmission. The bridge 7 can assign access slots so thatglobal and local transmissions do not conflict with each other. Thus,certain advantages may be obtained in the instance that the bridge 7 hasnetwork master capability. In this example embodiment, the CPU,operating under program control, can operate to configure the bridge 7as a master. In this case, the CPU serves as a beacon generator thatgenerates beacon signals transmitted over the first and second powerline circuits.

There may be an interference issue caused by the same frequencies on L1and L2, however, there are solutions for this problem. One istransmission power control. In this case, each device has automatic gaincontrol capability in AFE 502. The transmitter can minimize (optimize)transmission power level. This will reduce interference to the otherpower line. Another solution is to avoid troublesome frequencies thatcause interference. OFDM (Orthogonal Frequency Division Multiplex) maybe utilized in PLC systems. OFDM uses more than 100 sub-carriers. Somesub-carriers may cause substantial interference and some will not. Itmainly depends on the powerline layout. The transmitter and the receiveroften exchange a tone map. The tone map indicates which sub-carriers canbe used based on the result of signal-to-noise ratio (SNR) measurement.Based on the tone map, the transmitter selects sub-carriers andmodulation schemes. A poor SNR sub-carrier is eliminated or a robustmodulation (ex. Binary Phase Shift Keying) is used for the sub-carrier.This tone map mechanism avoids troublesome sub-carriers.

Referring now to FIG. 8, it is noted by the dashed arrows that there aretwo additional paths (besides the distribution transformer) that across-phase signal can take in order to pass from line L1 to L2 (andvice versa). Coupling can occur at the breaker board 5 as previouslydiscussed. In addition, a 240-volt appliance 13 may pass the signal fromline L1 to L2. The third path is by way of the distribution transformer1, but usually the transformer 1 is far and signal attenuation may bemuch greater than the other paths. The 240-volt appliance, for example,a laundry dryer is plugged into both L1 and L2. In order to minimizeinterference between the two circuits L1 and L2, it is desirable toblock both all paths from L1 to L2 at the frequencies of interest in thePLC network.

As shown in FIG. 1, the paths provided by the distribution transformerand the breaker board are blocked by the low pass filter 6. The 240VACappliance path can be blocked by the low pass filter 1001 shown in FIG.9. The Filter 1001 can be realized as, for example, AC plug adapterwhich is inserted between the power lines and the 240VAC appliance 13.The filter 1001 is designed to block all PLC signals and isolate L1 andL2. Since the 240VAC signal is at a very low frequency (60 Hz in theU.S.) and the PLC signals are generally at a far greater frequency(e.g., 1 to 30 MHz range), the design of an appropriate filter isreadily within the realm of conventional analog filter design, and thedetails of an exemplary filter circuit design need not be provided.Other embodiments will occur to those skilled in the art uponconsideration of the present teachings.

As previously mentioned briefly, bridging between two sets of powerlines supplied from separate distribution transformers may beaccomplished using wireless technology. FIG. 10 depicts a wirelessvariation of the bridge system shown in FIG. 4 used to accomplish asimilar function. Bridge A 901 and Bridge B 902 provide the wirelessbridge function by performing wireless communications between the uppercircuit 200 and the lower circuit 300. This application is particularlyuseful when the two powerline systems 200 and 300 are not so physicallyclose so as to enable easy connection with a wired bridge.

FIG. 11 shows an exemplary block diagram of the bridge 901 or 902.Except for the wireless interfaces, this bridge operates much the sameas that of FIG. 6. This embodiment adds MAC block 620, the physicallayer block 622, the analog frontend (RF transceiver) block 624 and theantenna 626 to the original block diagram shown in FIG. 6. Communicationbetween the two powerline systems 200 and 300 is carried out using thewireless interface as shown. The wireless communication can be carriedout using, for example, an IEEE 802.11 wireless network. For example,the device 208 sends a stream to the device 309. The stream is sent tothe bridge A 901. In the bridge A 901, the signal is processed from 501to 506 and forwarded to the wireless block 620 to 626 for wirelesscommunication. In the bridge B 902, the signal is received by theantenna 626, processed at the block 622 and 620 and forwarded to theblock 515 to 510. Finally, the signal is sent to the device 309 on theL2 power line. Note that the L2 line of 200 and the L1 line of 300 arecompletely isolated from this communication, and thus, lose nobandwidth.

In accordance with certain embodiments consistent with the presentinvention, certain advantages may be achieved such as the following: L1and L2 are isolated. Both buses will be used efficiently, up to twicebandwidth at best. The low pass filter isolates the in-home powerlinefrom the outside. The full powerline bandwidth is available. The filteralso reduces interference to the outside. No high transmission powerrequired for a global communication. Bandwidth is not reduced for aglobal communication. Interference can be minimized. The bridge relaysglobal communication. No serious attenuation occurs. The bridge mayefficiently assign an access slot to each transmitter so that the globalcommunication does not conflict with other local communications. Thebridge can be used for access powerline communication. The bridge can beused to link two or more independent power lines. While these and otheradvantages may be achieved using embodiments consistent with the presentinvention, failure to meet any of these advantages does not imply thatan embodiment falls outside the realm of other embodiments consistentwith the present invention.

PLC Breaker Bridge

To expand PLC bandwidth, the power line bridge described above uses across-phase PLC bridge. The bridge isolates L1 and L2 and theoreticallyexpands the bandwidth up to 200% of that available without the bridge.This concept can be further extended to take even greater advantage ofbandwidth re-use. In this extension of bandwidth re-use, a bridgeinstalled in the sub-breaker module isolates each branch line and blockslocal communications. In so doing, another branch line can re-use thesame time and frequency allocations and thus further increase thebandwidth available in any branch of the power line.

Powerline communication (PLC) is expected to be used as a backbone ofmany home networking. At this writing, the second generation PLCstandard is under discussion and will be soon finalized. The secondgeneration PLC as proposed is a 200 Mbps class network having an actualpayload rate of approximately 50 to 60 Mbps. This network is proposed tosimultaneously carry several MPEG-HD streams. Although the secondgeneration PLC meets present bandwidth requirements, more bandwidth willbe required when HDTV streaming becomes common.

In accordance with certain embodiments consistent with the presentinvention a bridge is designed for installation in a sub-breaker modulein order to isolate each branch line to block local communications whilepassing communication between branches. In this manner, multiple branchline can simultaneously use the same time and frequency allocations.

FIG. 12 illustrates exemplary powerline network. This is a single-phase3-line system. L1, L2 and the neutral line come from a distributiontransformer (not shown in FIG. 12). These lines go to the circuit's mainbreaker module 702 through the watt-hour meter 701. The dashed boxlabeled 702 can represent a breaker module housing in accordance withcertain embodiments consistent with the present invention. Breakerswitch contacts 721, 722 and 723 are normally closed. Contacts 721, 722and 723 are designed to open when electric current flowing to the home(or office, etc.) exceeds a threshold, for example 200 amps. The mainPLC unit 724 isolates the internal power lines from the incoming lines.The main PLC unit 724 also couples the cross-phase lines (L1 and L2).The power lines 711 and 712 are split into several branches (in thisexample, four branches L1 a, L1 b, L2 a and L2 b) after the main breakermodule 702.

Each branch line has a sub-breaker module shown as 703, 704, 705 and706. The dashed boxes surrounding the sub-breaker modules 703, 704, 705and 706 can be considered to represent a circuit breaker housing inaccordance with certain embodiments. PLC Bridge 731 works as a networkbridge, which isolates the branch line 707 (L1 a) from the L1 line 711and only passes necessary signals. The sub-breaker 732 is normallyclosed and will be open when electric current exceeds a thresholdestablished for the wiring of circuit L1 a, for example, 15 or 20 amps.The other sub-breaker module 704, 705 and 706 have the same internalcomponents. AC outlets 771 and 772 are connected to the branch line 707and serve both as sources of conventional AC power as well as connectionpoints for PLC devices. A PLC device can be plugged into any or all ofthe outlets. Usually, the main breaker module 702 and the sub-breakermodules (703, 704, 705 and to 706) are placed in the breaker board(i.e., circuit breaker panel).

Sub-breaker modules 704, 705 and 706 similarly contain PLC bridges 741,751 and 761, as well as sub-breakers 742, 752 and 762 respectively.Sub-breaker modules 704, 705 and 706 respectively supply branch lines708, 709 and 710 respectively which are also shown as branch lines L1 b,L2 a and L2 b respectively. Each of the branch lines can contain one ormore AC outlets. One pair is depicted on each branch line as 773 and774; 775 and 776; and 777 and 778.

FIG. 13 shows a block diagram of the internal components of the PLCBridge such as 731 (or 741, 751 or 761). The low pass filter 820 passesonly electric power (e.g., 120 Volt household current in the U.S.) andblocks PLC signals. Bridge 731 isolates the main lines (711 or 712) andthe branch lines (707, 708, 709 or 710) by use of a pair of transceivers(e.g., OFDM transceivers, HomePlug® compliant transceivers) that areisolated from each other by low pass filter 820, with signals passing toand from a branch from and to the main circuit at the MAC layer undercontrol of processor 808. A signal from the main line (L1 or L2) is sentto Analog Front End (AFE) 802 through Coupler 801. Coupler 801 blocks120 volt AC signals and only passes powerline network signals. Theoutput of AFE 802 is analog-to-digital converted in A/D 803 whichconverts analog signals to digital. The resulting output of 803 isprocessed in the physical layer block 805 and in Media Access Controllayer block 806. When a signal is sent to the main line, the signal isprocessed in the reverse direction. The signal is processed in MAC 806and in physical layer block 805. The result is digital-to-analogconverted in D/A 804 and sent to AFE 802 and Coupler 801. Components 810to 815 operate in the same manner as 801 to 806 for the local signalsappearing on the branch circuits. Processor (CPU) 808 controls thephysical and MAC layer blocks (805, 806, 814 and 815) through theinternal bus 807. The internal bus 807 is, for example, a PCI bus. CPU808 executes a software program stored in the read only memory 809. CPU808 uses the random access memory 816 for temporary storage.

When the data needs to be forwarded from the main line 711 to the branchline such as 707, the output of MAC 806 is sent to MAC 815 through theinternal bus 807. If data buffering is required as described later, CPU808 temporarily stores the data in RAM 816. Alternatively, the internalmemory in MAC 806 or 815 (not shown in FIG. 2) may store the data. Thepower supply block 830 obtains, for example, DC 5 volts from the ACvoltage and supplies to each component.

The PLC bridge 731 builds a table showing which physical address is onwhich segment (L1 line 711 or the branch L1 a). The table may be storedin the RAM 816 or other suitable storage device. The PLC Bridge 731blocks all the local communications between the AC outlet 771 and 772 toprevent such communications from passing to other branches and consumingbandwidth and time slots in the other branches. Such communicationsnever go outside of the branch Lla unless a device situated on anotherbranch is also addressed. The PLC Bridge 731 passes communications fromor to the device on another branch, for example, the AC outlet 773.Usually, most of the AC outlets in a room are on the same branch line orsituated close by. Thus, local communications in the room (e.g, from acomputer to a printer, or from a video source to a video player) stayson the branch line. By isolating the branches as described, the otherbranch lines can re-use the same time and frequency allocations forother communications, effectively increasing the network bandwidth.

In accordance with certain embodiments, the PLC bridge such as 731 ishoused within the housing of a circuit breaker module as is commonlyused household circuit breaker panels. Thus, installation is a simple asreplacement or substitution of a conventional circuit breaker with amodule containing a circuit breaker as well as a PLC bridge. While FIG.12 depicts the circuit breaker 732 as being situated on the branch sideof the PLC bridge, these components could also be reversed withoutdeparting from embodiments consistent with the present invention.

Note that the bridge 731 also performs a signal regeneration function.Usually, a signal from the remote device is attenuated, with attenuationincreasing with distance and line mismatches. By regenerating thesignal, the destination device receives the signal in good condition ona more frequent basis than would otherwise be obtained. This may beespecially significant in a PLC network where wiring conditions arerarely optimal for data communications. As a result, the networkcoverage may be extended. In addition, the bridge 731 isolates harmfulnoise on the other side, which is generated by appliances such as a hairdryer, a lamp dimmer, etc. The noise is blocked at the low pass filter720 to limit the effect of the noise source to the branch in which thenoise is created. The other branch lines are thereby kept cleaner ofsuch noise and interference.

In operation, determinations as to time slot and frequencies used forcommunications between branches can be determined in a manner similar tothat described above for the powerline network bridge.

FIG. 14 shows the internal components of the main PLC unit 724. The lowpass filter 891 blocks PLC signals to isolate the internal power lines711 and 712 from the incoming power lines. The coupler 892 passes PLCsignals between the L1 line 711 and the L2 line 712. The coupler 892 canbe as simple as an appropriately valued capacitor that appears as alarge impedance at power line frequencies (e.g., 60 Hz) and approximatesa short circuit at PLC communication frequencies. L1 and L2 signals canremain un-isolated within the main PLC unit 724.

FIG. 15 shows an alternative solution for the main PLC Bridge 724. Thecoupler 892 is replaced with the PLC bridge shown in FIG. 13. The Bridge724 isolates the L1 line 711 and the L2 line 712. The same bandwidth canbe re-usable on the cross-phase line. The low pass filter 901 can be thesame as low pass filter 891 in FIG. 14. The components 801 to 816 and830 are identical to those shown in FIG. 13.

In accordance with certain embodiments, all or many of the hardwarecomponents can be integrated into a few semiconductor chips, and thebridge can be implemented into a breaker module that is used in a mannersimilar to that of a conventional household circuit breaker with theadditional functionality of a PLC bridge incorporated therein. Also, inaccordance with other embodiments consistent with the present invention,the bridge (e.g., 731) may incorporate router functionality, whichfilters traffic by logical address.

Thus, in accordance with certain embodiments, a PLC breaker bridgeconsistent with certain embodiments may have one or more of thefollowing advantages: Each powerline branch is isolated and no localcommunication reaches the other branches. Network bandwidth will beefficiently re-used. An attenuated signal from the remote device isregenerated for improved error rate. The coverage may be extended. Noiseand interference generated on another branch line is isolated to asingle branch line. Thus, the other branches are clean and free of suchnoise interference. By implementing the bridge within a breaker module,only a module change is required for installation or replacement. No newbreaker board required. While these advantages may be present in certainembodiments, the failure of any or all of these advantages to be presentis not to be used as an indication of reading on the claims to follow.

Thus, a power line communication (PLC) bridge circuit, consistent withcertain embodiments, has a first coupler that couples data signals toand from a main power line circuit. A second coupler couples datasignals to and from a branch power line circuit, wherein the branchpower line circuit is branched from the main power line circuit. A firstcommunication transceiver is connected to the first coupler fortransferring data signals to and from the first coupler. A secondcommunication transceiver is connected to the second coupler fortransferring data signals to and from the second coupler. A controllerexamines data signals from the first transceiver and determines if thedata is destined for the second transceiver, so that data that is notdestined for the second transceiver is considered local data. Thecontroller also examines data signals from the second transceiver anddetermines if the data is destined for the first transceiver, so thatdata that is not destined for the first transceiver is also consideredlocal data. A bridge passes data signals between the first communicationtransceiver and the second transceiver when the controller determinesthat the data is not local, and passes data signals between the firstcommunication transceiver and the second communication transceiver whenthe controller determines that the data is local.

In certain embodiments consistent with the invention, the power linecommunication bridge circuit is housed within a housing that contains acircuit breaker. Thus, a circuit breaker can be coupled between the mainpower line circuit and the branch power line circuit. Certainembodiments also contemplates a coupler that couples PLC data betweenpower legs of the main power line circuit; and a low pass filter thatblocks PLC data from exiting a supply side of the main power linecircuit. The coupler and the low pass filter can be situated within amain power line circuit breaker. The bridge can include a common busthat is shared by the first and second communication transceivers,wherein the common bus is controlled by the controller. The first andsecond communication transceivers comprise orthogonal frequency divisionmultiplexing (OFDM) transceivers. The first and second communicationtransceivers can be HomePlug® standard compliant transceivers. Theprocessor can identify at least one of an available time slot and anavailable frequency for passing the data signal between the first andsecond communication transceivers. The power line communication bridgecircuit can also have a beacon generator that generates beacon signalstransmitted over the first and second power line circuits, wherein thepower line communication bridge circuit serves as a master in the PLCnetwork. The controller can determine whether or not the data is localby consulting a device table. The power line communication bridgecircuit consistent with certain embodiments, can further incorporate afilter that isolates the main power line circuit from the branch powerline circuit at frequencies used for power line communication. Any orall of these variations can be used interchangeably.

In accordance with another embodiment, a power line communication (PLC)bridge circuit has a first coupler that couples data signals to and froma main power line circuit and a second coupler that couples data signalsto and from a branch power line circuit. A first communicationtransceiver is connected to the first coupler for transferring datasignals to and from the first coupler. A second communicationtransceiver is connected to the second coupler for transferring datasignals to and from the second coupler. The first and secondcommunication transceivers can be HomePlug® standard complianttransceivers. A controller examines data signals from the firsttransceiver and determines if the data is destined for the secondtransceiver, wherein data that is not destined for the secondtransceiver is considered local data. The controller also examines datasignals from the second transceiver and determines if the data isdestined for the first transceiver, wherein data that is not destinedfor the first transceiver is also considered local data. A common bus isshared by the first and second communication transceivers, wherein thecommon bus is controlled by the controller. The controller also passesdata signals over the common bus between the first communicationtransceiver and the second transceiver when the controller determinesthat the data is not local, and does not pass data signals between thefirst communication transceiver and the second communication transceiverwhen the controller determines that the data is local, wherein thecontroller determines whether or not the data is local by consulting adevice table. The processor identifies at least one of an available timeslot and an available frequency for passing the data signal between thefirst and second communication transceivers. A filter isolates the firstand second power line circuits from each other at frequencies used forpower line communication. A circuit breaker is coupled between the mainpower line circuit and the branch power line circuit and the bridgecircuit is housed within a housing that contains a circuit breaker.

In accordance with another embodiment, a power line communication (PLC)bridge circuit has a first coupler that couples data signals to and froma main power line circuit and a second coupler that couples data signalsto and from a branch power line circuit. A first communicationtransceiver is connected to the first coupler for transferring datasignals to and from the first coupler. A second communicationtransceiver is connected to the second coupler for transferring datasignals to and from the second coupler. A controller examines datasignals from the first transceiver and determines if the data isdestined for the second transceiver, wherein data that is not destinedfor the second transceiver is considered local data. The controllerfurther examines data signals from the second transceiver and determinesif the data is destined for the first transceiver, wherein data that isnot destined for the first transceiver is also considered local data. Abridge circuit passes data signals between the first communicationtransceiver and the second transceiver when the controller determinesthat the data is not local, and does not pass data signals between thefirst communication transceiver and the second communication transceiverwhen the controller determines that the data is local. A circuit breakeris coupled between the main power line circuit and the branch power linecircuit, wherein the bridge circuit is housed within a housing thatcontains a circuit breaker.

In accordance with certain embodiments, the power line communicationbridge circuit described uses a common bus shared by the first andsecond communication transceivers, wherein the common bus is controlledby the controller, to pass data between the transceivers. The first andsecond communication transceivers comprise orthogonal frequency divisionmultiplexing transceivers which may be HomePlug® standard complianttransceivers. The processor may be used to identify at least one of anavailable time slot and an available frequency for passing the datasignal between the first and second communication transceivers. A beacongenerator can be provided to generate beacon signals transmitted overthe first and second power line circuits, wherein the power linecommunication bridge circuit serves as a master in the PLC network. Thecontroller can determine whether or not the data is local by consultinga device table, or can use any other suitable mechanism. The power linecommunication bridge circuit can further have a filter that isolates thefirst and second power line circuits from each other at frequencies usedfor power line communication.

A power line communication (PLC) bridging method consistent with certainembodiments involves receiving data from a main power line circuit and abranch power line circuit branching from the main power line circuit;examining data signals from the branch power line circuit to determineif the data is destined for the branch power line circuit, and if so notpassing the data to the main power line circuit, and if not then passingdata to the main power line circuit; and examining data signals from themain power line circuit to determine if the data is destined for thebranch power line circuit, wherein if the data is destined for thebranch power line circuit then passing the data to the branch power linecircuit and if not, the then not passing data to the branch power linecircuit.

In certain embodiments of the method, the data signals are passed over acommon bus shared by first and second communication transceivers. Thedata signals may comprise orthogonal frequency division multiplexedsignals. The data signals may be HomePlug® standard compliant datasignals. The power line communication method can further involveidentifying at least one of an available time slot and an availablefrequency for passing the data signal between the first and second powerline circuit. The destination of the data can be determined byconsulting a device table. The method can further involve determining ifan amount of current passing to the branch circuit exceeds a threshold,and if so, opening a circuit breaker. The method can be carried outwithin a device that houses both a circuit breaker and a power linecommunication bridge. The device that houses both the circuit breakerand the power line communication bridge can be a circuit breaker modulehousing. The method can be carried out using a computer readable storagemedium storing instructions which, when executed on a programmedprocessor, carry out the process.

Those skilled in the art will recognize, upon consideration of the aboveteachings, that certain of the above exemplary embodiments are basedupon use of a programmed processor such as CPU 508 or 808. However, theinvention is not limited to such exemplary embodiments, since otherembodiments could be implemented using hardware component equivalentssuch as special purpose hardware and/or dedicated processors. Similarly,general purpose computers, microprocessor based computers,micro-controllers, optical computers, analog computers, dedicatedprocessors, application specific circuits and/or dedicated hard wiredlogic may be used to construct alternative equivalent embodiments.

Those skilled in the art will appreciate, upon consideration of theabove teachings, that the program operations and processes andassociated data used to implement certain of the embodiments describedabove can be implemented using disc storage as well as other forms ofstorage such as for example Read Only Memory (ROM) devices, RandomAccess Memory (RAM) devices, network memory devices, optical storageelements, magnetic storage elements, magneto-optical storage elements,flash memory, core memory and/or other equivalent volatile andnon-volatile storage technologies without departing from certainembodiments of the present invention. Such alternative storage devicesshould be considered equivalents.

Certain embodiments described herein, are or may be implemented using aprogrammed processor executing programming instructions that are broadlydescribed above in flow chart form that can be stored on any suitableelectronic or computer readable storage medium and/or can be transmittedover any suitable electronic communication medium. However, thoseskilled in the art will appreciate, upon consideration of the presentteaching, that the processes described above can be implemented in anynumber of variations and in many suitable programming languages withoutdeparting from embodiments of the present invention. For example, theorder of certain operations carried out can often be varied, additionaloperations can be added or operations can be deleted without departingfrom certain embodiments of the invention. Error trapping can be addedand/or enhanced and variations can be made in user interface andinformation presentation without departing from certain embodiments ofthe present invention. Such variations are contemplated and consideredequivalent.

While certain embodiments herein were described in conjunction withspecific circuitry that carries out the functions described, otherembodiments are contemplated in which the circuit functions are carriedout using equivalent software or firmware embodiments executed on one ormore programmed processors. General purpose computers, microprocessorbased computers, micro-controllers, optical computers, analog computers,dedicated processors, application specific circuits and/or dedicatedhard wired logic and analog circuitry may be used to constructalternative equivalent embodiments. Other embodiments could beimplemented using hardware component equivalents such as special purposehardware and/or dedicated processors.

While certain illustrative embodiments have been described, it isevident that many alternatives, modifications, permutations andvariations will become apparent to those skilled in the art in light ofthe foregoing description.

1. A power line communication (PLC) bridge circuit, comprising: a firstcoupler that couples data signals to and from a main power line circuit;a second coupler that couples data signals to and from a branch powerline circuit, wherein the branch power line circuit is branched from themain power line circuit; a first communication transceiver connected tothe first coupler for transferring data signals to and from the firstcoupler; a second communication transceiver connected to the secondcoupler for transferring data signals to and from the second coupler; acontroller that examines data signals from the first transceiver anddetermines if the data is destined for the second transceiver, whereindata that is not destined for the second transceiver is considered localdata; the controller further examines data signals from the secondtransceiver and determines if the data is destined for the firsttransceiver, wherein data that is not destined for the first transceiveris also considered local data; and bridging means for passing datasignals between the first communication transceiver and the secondtransceiver when the controller determines that the data is not local,and for not passing data signals between the first communicationtransceiver and the second communication transceiver when the controllerdetermines that the data is local.
 2. The power line communicationbridge circuit in accordance with claim 1, wherein the bridge circuit ishoused within a housing that contains a circuit breaker.
 3. The powerline communication bridge circuit in accordance with claim 1, furthercomprising a circuit breaker, coupled between the main power linecircuit and the branch power line circuit.
 4. The power linecommunication bridge circuit in accordance with claim 1, furthercomprising a coupler that couples PLC data between power legs of themain power line circuit; and a low pass filter that blocks PLC data fromexiting a supply side of the main power line circuit.
 5. The power linecommunication bridge circuit in accordance with claim 1, wherein thecoupler and the low pass filter are situated within a main power linecircuit breaker.
 6. The power line communication bridge circuit inaccordance with claim 1, wherein the bridging means for passing datasignals comprises a common bus shared by the first and secondcommunication transceivers, wherein the common bus is controlled by thecontroller.
 7. The power line communication bridge circuit in accordancewith claim 1, wherein the first and second communication transceiverscomprise orthogonal frequency division multiplexing (OFDM) transceivers.8. The power line communication bridge circuit in accordance with claim1, wherein the first and second communication transceivers compriseHomePlug® standard compliant transceivers.
 9. The power linecommunication bridge circuit in accordance with claim 1, wherein theprocessor identifies at least one of an available time slot and anavailable frequency for passing the data signal between the first andsecond communication transceivers.
 10. The power line communicationbridge circuit in accordance with claim 1, further comprising a beacongenerator that generates beacon signals transmitted over the first andsecond power line circuits, wherein the power line communication bridgecircuit serves as a master in the PLC network.
 11. The power linecommunication bridge circuit in accordance with claim 1, wherein thecontroller determines whether or not the data is local by consulting adevice table.
 12. The power line communication bridge circuit inaccordance with claim 1, further comprising a filter that isolates themain power line circuit from the branch power line circuit atfrequencies used for power line communication.
 13. A power linecommunication (PLC) bridge circuit, comprising: a first coupler thatcouples data signals to and from a main power line circuit; a secondcoupler that couples data signals to and from a branch power linecircuit; a first communication transceiver connected to the firstcoupler for transferring data signals to and from the first coupler; asecond communication transceiver connected to the second coupler fortransferring data signals to and from the second coupler; wherein thefirst and second communication transceivers comprise HomePlug® standardcompliant transceivers; a controller that examines data signals from thefirst transceiver and determines if the data is destined for the secondtransceiver, wherein data that is not destined for the secondtransceiver is considered local data; the controller further examinesdata signals from the second transceiver and determines if the data isdestined for the first transceiver, wherein data that is not destinedfor the first transceiver is also considered local data; a common busshared by the first and second communication transceivers, wherein thecommon bus is controlled by the controller; wherein the controllerfurther passes data signals over the common bus between the firstcommunication transceiver and the second transceiver when the controllerdetermines that the data is not local, and for not passing data signalsbetween the first communication transceiver and the second communicationtransceiver when the controller determines that the data is local,wherein the controller determines whether or not the data is local byconsulting a device table; wherein the processor identifies at least oneof an available time slot and an available frequency for passing thedata signal between the first and second communication transceivers; afilter that isolates the first and second power line circuits from eachother at frequencies used for power line communication; and a circuitbreaker, coupled between the main power line circuit and the branchpower line circuit, wherein the bridge circuit is housed within ahousing that contains a circuit breaker.
 14. A power line communication(PLC) bridge circuit, comprising: a first coupler that couples datasignals to and from a main power line circuit; a second coupler thatcouples data signals to and from a branch power line circuit; a firstcommunication transceiver connected to the first coupler fortransferring data signals to and from the first coupler; a secondcommunication transceiver connected to the second coupler fortransferring data signals to and from the second coupler; a controllerthat examines data signals from the first transceiver and determines ifthe data is destined for the second transceiver, wherein data that isnot destined for the second transceiver is considered local data; thecontroller further examines data signals from the second transceiver anddetermines if the data is destined for the first transceiver, whereindata that is not destined for the first transceiver is also consideredlocal data; bridging means for passing data signals between the firstcommunication transceiver and the second transceiver when the controllerdetermines that the data is not local, and for not passing data signalsbetween the first communication transceiver and the second communicationtransceiver when the controller determines that the data is local; and acircuit breaker, coupled between the main power line circuit and thebranch power line circuit, wherein the bridge circuit is housed within ahousing that contains a circuit breaker.
 15. The power linecommunication bridge circuit in accordance with claim 14, wherein themeans for passing data signals comprises a common bus shared by thefirst and second communication transceivers, wherein the common bus iscontrolled by the controller.
 16. The power line communication bridgecircuit in accordance with claim 14, wherein the first and secondcommunication transceivers comprise orthogonal frequency divisionmultiplexing transceivers.
 17. The power line communication bridgecircuit in accordance with claim 14, wherein the first and secondcommunication transceivers comprise HomePlug® standard complianttransceivers.
 18. The power line communication bridge circuit inaccordance with claim 14, wherein the processor identifies at least oneof an available time slot and an available frequency for passing thedata signal between the first and second communication transceivers. 19.The power line communication bridge circuit in accordance with claim 18,further comprising a beacon generator that generates beacon signalstransmitted over the first and second power line circuits, wherein thepower line communication bridge circuit serves as a master in the PLCnetwork.
 20. The power line communication bridge circuit in accordancewith claim 14, wherein the controller determines whether or not the datais local by consulting a device table.
 21. The power line communicationbridge circuit in accordance with claim 14, further comprising a filterthat isolates the first and second power line circuits from each otherat frequencies used for power line communication.
 22. A power linecommunication (PLC) bridging method, comprising: receiving data from amain power line circuit and a branch power line circuit branching fromthe main power line circuit; examining data signals from the branchpower line circuit to determine if the data is destined for the branchpower line circuit, and if so not passing the data to the main powerline circuit, and if not then passing data to the main power linecircuit; and examining data signals from the main power line circuit todetermine if the data is destined for the branch power line circuit,wherein if the data is destined for the branch power line circuit thenpassing the data to the branch power line circuit and if not, the thennot passing data to the branch power line circuit.
 23. The power linecommunication method in accordance with claim 22, wherein the datasignals are passed over a common bus shared by first and secondcommunication transceivers.
 24. The power line communication method inaccordance with claim 23, wherein the data signals comprise orthogonalfrequency division multiplexing signals.
 25. The power linecommunication method in accordance with claim 23, wherein the datasignals comprise HomePlug® standard compliant data signals.
 26. Thepower line communication method in accordance with claim 22, furthercomprising identifying at least one of an available time slot and anavailable frequency for passing the data signal between the first andsecond power line circuit.
 27. The power line communication method inaccordance with claim 22, wherein the destination of the data isdetermined by consulting a device table.
 28. The power linecommunication method in accordance with claim 22, further comprisingdetermining if an amount of current passing to the branch circuitexceeds a threshold, and if so, opening a circuit breaker.
 29. Themethod according to claim 29, carried out within a device that housesboth a circuit breaker and a power line communication bridge.
 30. Themethod according to claim 29, wherein the device that houses both thecircuit breaker and the power line communication bridge comprises acircuit breaker module housing.
 31. A computer readable storage mediumstoring instructions which, when executed on a programmed processor,carry out a process in accordance with claim 22.